Two systems are being analyzed as keys to gene regulation in eucaryotes: the change from tadpole to adult frog hemoglobin in the bullfrog, Rana catesbeiana, and the production of LDH X in postmeiotic sperm of mammals, especially man. In both systems there is change in a specific gene product at one point in development. The thrust of the research is to find specific biological molecules which are responsible for this specific inactivation of tadpole homoglobin genes and activation of frog hemoglobin (or LDH X) genes. To this end, cell-free systems are being developed from both the tadpole erythrocyte and the mammalian sperm systems. The cell-free systems are analyzed for production of their specific gene products, and then various factors are added in an attempt to alter such production.